Part 2 of the rough idle/hesitation diagnosis video.
Part 1 can be found here:
https://www.youtube.com/watch?v=yMd89_DAA_4
DIY 02 Ford Rough Idle Diagnosis With a Twist! Pt2
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Do both your software based scan tools use a wireless dongle? I've had problems with the elm wireless connectors not behaving properly. I wonder if a wired cheapy scan tool would show any differently?
I don't think a smoke machine is cheating for a DIY'er. My smoke machine is one of those large Christmas popcorn tins with a smaller bread tin ($1 from the dollar store) inside holding a lit charcoal briquette surrounded by baby oil. Two air couplers installed in the tin lid. One hooked up to air compressor on lowest setting, the other is the smoke hose. Hillbilly but it works -LOL! Found plenty of vacuum leaks in an old expedition which uses tons of vacuum hoses. Even the AC control unit is controlled by vacuum lines. Worse vehicle I've ever owned! Hate Fords.
My guess is that some vehicles are mapped for a single total fuel trim in each bank and for this vehicle that total fuel trim defaults to short term fuel trim on scanners. Maybe there is a part number on the pcm that could be researched or a service manual for the vehicle.
I think you have something screwed up in the PCM programming, I have seen a similar issue to this on a vehicle that I purchased once.
It was an Acura 2.5 TL, long story short the programming in the PCM somehow got corrupted I think because of a bad alternator at some point. The long-term wouldn't correct and the short-term was just stuck at +8.5. The engine ran like shit and after 3 different shops couldn't figure it out and they sold it and I bought it.
You could see that the parts Cannon had been just absolutely unloaded on this thing, I thought the readings on the PCM or weird so I took a chance and bought a used one and installed it and the thing ran perfect for years until I sold it!
The car had a brand new alternator and a brand new battery leading me to believe that at some point the alternator must have failed and maybe send some sort of voltage Spike through the system and killed the PCM I don't know the car still ran just not correctly and the programming was clearly corrupted???
I was hoping you would chase the dash lights, it just seems weird that they came on, especially without any airbag code. Could it all lead to a bad ending resistor or sth weird like that?
And if the scan-tool can't display the injector time, then hook up a PicoScope or an 8 channel cheap Hantek 1008c scope and get a direct reading of an injector pulse, and maybe there are known good waveforms at PicoScope's online library…
The short answer: we don't need the values of LTFT on the scanner to know if it is positive or negative, we just need the injector time and compare it to the factory specs, and then do the calculation ourselves…
Well one must assume that the computer can calculate, and adjust, LTFT since the STFT zeroes in when You introduce the vacuum leak or add propane. It just can't communicate it to the scanner. But the computer must know the value, and adjust the injector time, because SHTF and LTFT percentages are just values for how many percentages the injector time is changed. How do we then know how big the LTFT correction is? Well if You pull up the PID's for injector time, and compare them with factory specs or a known good, then we should be able to calculate the percentage of LTFT correction and see how it reacts to vacuum leak/propane and where it settles when the STFT is around zero percentage. There must be somewhere we can obtain the nominal value of the injector time for a known good engine, either from the factory manual, or someone with the same engine in good working condition….
I know that on these Fords disconnecting the Neg cable won't clear the capacitors. Connecting a wire with alligator clips on each end from the disconnected Neg cable to the connected Pos cable for 5 minutes will clear the capacitors and reset the learned driving habit trends such as shift points, idle position for throttle body, everything. Made a huge difference for me Matt. After reconnecting the battery turn the key on and leave for 15 seconds, then start and idle the car in park for 10 minutes. Then go for a drive. Nice and easy. The CPU will relearn the valves that were previously stored. You probably know this but thought I'd mention it.
Wow….. never seen anything like this. Great video as usual Matt.
your point about dielectric grease is salient, it is an insulating grease… it prevents ingress of water and outgress of high voltage spark. the only time I recommend putting on an electrical connector is maybe on top of an earth to chassis bolt where there's evidence of prior corrosion just to prevent further corrosion… notice I said on top, not between… metal should be contacting metal.
That there truck has brain damage. Solved
Could you use a break out box with your scope and see if you have any weird glitches in the network
New info about dielectric grease. Ty. Never use but good to know how to use properly
This reminds me of the days when I was the responsible technician to calibrate the MFAC (main fuel actuator control) on a Solar International industrial natural gas turbine. The MFAC was an analog computer that worked to control the fuel to the turbine engine. In all control modes the output of the MFAC was a current signal (10 – 50 mA) to the Fuel Throttle. The MFAC did not have separate long and short trims, but rather combined the outputs of three different analog computations into one. The three analog computations were Proportional & Integral & Differential based on the controlling setpoint signal. It seems that you have been blessed with an ECU that apparently combined long and short term fuel trims together to get the needed “overall” fuel trim.
Assuming that this vehicle had a MAP sensor, I kept waiting for you to pull up that P.I.D. for clues. As you well know, the MAP sensor ideally reflects intake manifold pressure and could be used to diagnose vacuum leaks real time using a scanner. Just thinking out loud. Hope this helps?
I suspect if the engine was swapped the PCM may have also been swapped with it. That would explain the PIDs not mapping correctly – for example, it may be reading PID 32 & 33 when this PCM broadcasts that data on PID 35 & 36 (this is an arbitrary example).
Those perfectly round numbers for the STFT don't look right to me, either. It makes me wonder if it's using a default fuel map for some reason. What a bugger. Great that it works better, but now it'll bug you until you work it out. 🙂
Hey Matt, you might try Forscan next time you need to work on a Ford, free software that is damn near a dealership-level scan tool for any Ford (and supposedly Mazdas, though I have not tried it on a Mazda yet).
I would be interested to see if Forscan would have actually read the PIDs on this expedition correctly, though I assume we won't see it for a while unless the customer wants to diagnose the dash lights.
As you said I would be very suspicious of previous mechanic involvement. Who knows what things they screwed with, the ghost dash lights are a very good indication I think that there is something electrically wrong thus affecting the reporting of the LTFTs
Another weird thing I noticed was the digital odometer wasn't on until you put it into gear at 28:41. Definitely some weird electrical issues going on. I see some wire diagrams and a lab scope in the future if you follow up. Would definitely be a very interesting case study. Probably not DIY friendly though lol.